4. CONCLUDING REMARKS

It is impressive to see how well the Friedmann-Lemaître model fits
the full range of observations summarized in
Table 2. We have to to bear in mind
that many of the measurements still are open to
discussion, however, and that the entries in category 2 depend on a
model for structure formation that also has to be tested. Thus there is
a large number of question marks (even though I believe I have been an
easy grader). Perhaps the best lesson one might draw from the length of
the discussion of Table 2 in
Section 3 is that we theorists ought to resist
the temptation to draw large conclusions from the latest observational
reports; these are extraordinarily difficult measurements that we best
praise by respectful cautious consideration.

I think we should also bear in mind that substantial parts of the
left-hand column of Table 1 were
formulated a full seven decades ago,
and that much of the rest was driven by observational advances. That is,
although we have many elegant new theoretical ideas in cosmology, we
have little evidence in hand on which Nature has chosen.

The right-hand column of Table 1,
that represents the observational
constraints, is considerably longer than it would have been in a list
made ten years ago, and ten years ago there would have been a lot more
question marks in Table 2. We can be
sure work in progress will produce
a considerably tighter network of cosmological tests ten years from now. I
see no reason to think the results will fail to support the
Friedmann-Lemaître model, but
that will be revealed in the fullness of time and a lot of hard work.

Acknowledgements

I am grateful to David Hogg, Wayne Hu, and Max Tegmark for stimulating
discussions. This work was supported in part at the Princeton Institute
for Advanced Study by the Alfred P. Sloan Foundation.